One-step removal of alkynes and propadiene from cracking gases using a multi-functional molecular separator

Refineries generally employ multiple energy-intensive distillation/adsorption columns to separate and purify complicated chemical mixtures. Materials such as multi-functional molecular separators integrating various modules capable of separating molecules according to their shape and chemical properties simultaneously may represent an alternative. Herein, we address this challenge in the context of one-step removal of alkynes and propadiene from cracking gases (up to 10 components) using a multi-functional and responsive material ZU-33 through a guest/temperature dual-response regulation strategy. The responsive and guest-adaptive properties of ZU-33 provide the optimized binding energy for alkynes and propadiene, and avoid the competitive adsorption of olefins and paraffins, which is verified by breakthrough tests, single-crystal X-ray diffraction experiments, and simulation studies. The responsive properties to different stimuli endow materials with multiple regulation methods and broaden the boundaries of the applicability of porous materials to challenging separations.


Materials and Reagents
All reagents and solvents were commercially purchased and used without further purification.
Then, the mixture was heated at 80 °C for 12 h. The obtained powder was filtered, washed with methanol, and exchanged with methanol for 3 days 2,3 .
Then, the mixture was heated at 80 °C for 12 h. The obtained powder was filtered, washed with methanol, and exchanged with methanol for 3 days 2,3 .

Single crystal X-ray diffraction
Single crystal X-ray diffraction data for ZU-33 were collected on a Bruker D8 VENTURE diffractometer equipped with a PHOTONII/CMOS detector (GaKα, λ =1.314139 Å). Indexing was performed using APEX3. Data integration and reduction were completed using SaintPlus 6.01. Absorption correction was performed by the multi-scan method implemented in SADABS. The space group was determined using XPREP implemented in APEX3. The structure was solved with SHELXS-2018 (direct methods) and refined on F2(nonlinear least-squares method) with SHELXL-2018 contained in APEX3 program packages. All non-hydrogen atoms were refined anisotropically. Firstly, the ZU-33 single crystals were loaded into the sample tube for adsorption test, the inner wall of the sample tube was coated with oil (polybutenes), which slowly flowed down the tube wall. Then, C2H2 and C3H4 gas was backfilled, respectively. After ZU-33 single crystals were sealed by oil, they were taken out and tested on a Bruker D8 VENTURE diffractometer.

Breakthrough experiments
The breakthrough experiments were carried out in a dynamic gas breakthrough equipment 2 . All experiments were conducted using a stainless steel column (4.6 mm inner diameter × 50 mm). According 5 to the different particle size and density of the sample powder, the weight packed in the column was: also relaxed as references. Then, the guest molecules were introduced onto the host surface and different 6 locations in the channel pore of the host structure, respectively, followed by a full structural relaxation.
And the optimized configurations having the lowest energy were used for the subsequent analysis and calculation. The transition state search calculations were used to capture the transition statues associated with guest transport between the two know energy minimum configurations from the host surface to the channel pore. The initial state I was defined as the optimized guest-free host and optimized guest, and the system energy was set as the reference. The state II was defined as the optimized host-guest structures where guests were introduced onto the host surface, the state III was defined as the transition state and the state IV was defined as the optimized host-guest structures where guests were introduced into the channel pore. The energy barrier was calculated using: where E (state III) is the energy of the transition state, E (state II) is the energy of the optimized hostguest structures where guests were introduced onto the host surface.
The static binding energy. The static binding energy (at T=0 K) was calculated using: where E (MOF) is the energy of the optimized guest-free host, E (gas) is the energy of the optimized guest and E (MOF+ gas) is the total energy of the optimized host-guest structures. involves the "parabola" like sudden temperature change, like C2 part, the temperature in hydrogenation process is ca 100 °C, while in distillation column, it is -16/-30 °C, thus, a substantial energy input is

Supplementary Tables
Supplementary Table 1